1. Field of the Invention
The subject invention relates to a stopper for a needle of a syringe such as an arterial blood gas syringe, and more particularly to a stopper which enables one-handed covering and sealing of the needle, and a subsequent safe separation and containment of the needle from the syringe barrel.
2. Description of the Prior Art
A hypodermic syringe includes a syringe barrel having an open proximal end and an opposed distal end. A cylindrical wall extends between the proximal and distal ends and defines a fluid receiving chamber in the syringe barrel. The distal end of the syringe barrel includes a passage that extends therethrough and communicates with the chamber. The distal end also is configured to receive a needle cannula which communicates with the passage and the chamber. The prior art hypodermic syringe also includes a plunger in sliding fluid tight engagement with the cylindrical wall of the chamber. Sliding movement of the plunger toward the distal end causes fluid in the chamber to be evacuated through the passage and the needle cannula. Conversely, sliding movement of the plunger toward from the proximal end draws fluid through the needle cannula and the passage and into the chamber.
Most hypodermic needles are provided with needle shields or covers to protect the needle from damage and contamination during shipment and transfer to the patient's room as well as to protect health care workers from accidental needle sticks involving clean unused needles. The needle shield or cover typically is removed immediately prior to use of the hypodermic syringe. A hypodermic syringe that is used for an injection typically will be discarded into a special sharps collector immediately after injection to further protect against accidental needle sticks. However, hypodermic syringes such as arterial blood gas syringes that are used to withdraw fluid from a patient cannot be discarded until the fluid has been properly evaluated. To protect against accidental needle sticks at this stage, the needle cannula may be removed or covered with a needle stopper.
Some medical procedures require periodic sampling and evaluation of arterial blood. For example, blood may be evaluated for content of carbon dioxide, oxygen and pH. Arterial blood may also be evaluated for concentration of electrolytes, such as sodium and potassium.
An arterial blood gas syringe is similar to a hypodermic syringe but it also includes an anticoagulant such as liquid or dry heparin in the chamber to prevent blood clotting. Also, an arterial blood gas syringe usually contains means associated with the plunger which allows gas, such as air, to leave the chamber but blocks the exit of liquid such as blood.
The use of an arterial blood gas syringe for arterial blood gas analysis is difficult for several reasons. Arteries often are deeper in the body of the patient, and hence more difficult to locate. Accordingly, the respiratory therapist, technician or phlebotomist must insert the needle fairy deeply, thereby causing considerable discomfort to the patient. After removal of syringe from the patient, the therapist must immediately apply pressure to the punctured artery to prevent bleeding. Proper evaluation of arterial blood gas requires prompt sealing of the arterial blood sample to prevent reaction of the blood with ambient air. However, the realities of the procedure often require the respiratory therapist to use one hand for applying pressure to the puncture wound, thereby leaving only one hand to seal the needle cannula and to handle the blood filled syringe.
The prior art includes arterial blood gas syringe kits with components to seal the needle cannula after withdrawal from the patient. In particular, a prior art kit includes an arterial blood gas syringe and a cube of rubber, plastic or cork approximately 1 cm.sup.3. The therapist usually places the cube on a flat surface near the patient. An arterial blood sample then is obtained in the standard manner. After withdrawing the needle cannula from the patient, the therapist applies pressure to the wound with one hand, while using the other hand to urge the tip of the needle cannula into the cube on the work surface near the patient. The cube occludes the needle cannula to prevent blood/air interaction while the respiratory therapist attends to the hemostasis. The therapist then shakes the syringe to mix the blood and the heparin anticoagulant in the syringe barrel. The needle is then removed by using a hemostat or by hand, and the used needle is discarded into an appropriate safety collector for sharp objects. The syringe tip then is covered with a tip cap. The blood filled syringe with tip cap is usually placed in a container including ice and sent to a laboratory for analysis.
The prior art arterial blood gas kit has several disadvantages. For example, the small rubber cube neither guides nor limits the movement of the needle. Thus, the needle can be skewed during insertion by the respiratory therapist or it can bend during insertion to project from a side surface of the small rubber cube. Similarly, the small cube can tilt during insertion thereby enabling the tip of the needle to pass entirely through the cube. In either case, the tip of the needle is exposed and enables ambient air to react with the arterial blood in the syringe. Furthermore, the exposed tip of the needle can lead to accidental needle stick. Means for removing the needle from the syringe barrel may reduce the risk of accidental needle stick, but a separate removal means in the arterial blood gas kit adds to the complexity.
As noted above, the prior art also includes many types of needle shields that can be placed over the needle to prevent accidental puncture. However, these prior art needle shields generally do not occlude the needle tip, and generally are not well suited for the one-handed sealing that is realistically required for arterial blood gas procedures.